This invention relates to weight lifting, or bodybuilding, equipment and particularly to apparatus using free weights to build up the biceps by performing an exercise known to bodybuilders as curling.
The exercise of curling can be performed using a long bar held horizontally by both hands near the ends or a short bar held horizontally in one hand. In either case, the exercise consists in moving the weighted bar in an arc from a lower position, usually near the bodybuilder's thighs, to an upper position near his shoulders. For the sake of simplicity, the following description will assume that the bar is a long one held in both hands.
The bodybuilder is supposed to keep his elbows approximately immobile and to move only his forearms and hands. The biceps have to exert the greatest force when the bar is in the mid region of the arc, since in that region, the motion of the bar is almost entirely vertical with a very small horizontal component. At the upper part of the arcuate movement, when the bodybuilder's hands and the weight bar held by them are moving more nearly horizontally than vertically to bring the bar near the bodybuilder's shoulders, the biceps are under relatively little stress. Bodybuilders speak of this position as a resting position because the biceps are not being stressed in a way that is considered beneficial in building up strength or musculature.
It has been proposed heretofore to shift the location of the center of mass of the weights so as not to be in line with the part of the bar held by the bodybuilder's palms. U.S. Pat. No. 4,327,908 to James discloses bodybuilding apparatus in which the part of the apparatus to which the weights are attached is positioned over the portion of the bodybuilder's forearms adjacent his wrists while an offset bar is held in the weight lifter's hands. This actually reduces the effect of the weights, since it brings the center of mass closer to the bodybuilder's elbow and thus gives an effect similar to using smaller weights held in the bodybuilder's hands.
U.S. Pat. No. 4,7565,526 to Broussard shows a different exercise device that has a sleeve rotatably mounted on a bar between two weights. The bar can pass through either of two holes in the weights, one of which is close to the center of mass of that weight and the other of which is near a part of the perimeter as far away from the center of mass as is possible. Inserting the ends of the bar into the latter holes offsets the center of mass, and the rotatable sleeve allows the weights to hang down during the exercise. In order to limit the freedom of rotation of the weights and force them to project forward when the bodybuilder's arms are near his shoulders, Broussard provides a second bar, called a leverage bar, that passes through another hole located in a part of each of the weights close to the center of mass but offset to one side thereof and in a fixed position relative to the center of mass. As the apparatus is moved through an arcuate path, a point is reached where the leverage bar engages the backs of the bodybuilders forearms, and from that point on through the rest of the arc, the leverage bar prevents any further turning motion of the weights relative to the main bar. The fact that the point at which the leverage bar becomes effective to prevent further rotation of the weights is fixed makes it impossible to change the effective force produced on the bodybuilder's biceps by adjusting that point or by changing the range over which the leverage bar will be effective. Moreover, the location of the leverage bar is such that, when it comes into use, the center of mass of the weights is closer to the bodybuilder's elbows than is the bar from which the weights are suspended. Thus, the effect on the bodybuilder is similar to the effect of using smaller, not larger, weights. In addition, the leverage bar is not in contact with the bodybuilder's forearms at all times but can pivot rather suddenly to strike them, which can be painful and even dangerous.
U.S. Pat. No. 4,231,569 to Rae shows apparatus that has certain similarities to the Broussard device. As in that device, the apparatus of Rae has a main bar held in the bodybuilder's hands and a second bar or structure offset therefrom to engage the backs of the bodybuilder's forearms after a certain point is reached during the arcuate movement of the main bar. Rae's structure is arranged so that the center of mass is out beyond the bodybuilder's hands during the upper part of the arcuate movement of the device, and this stresses his biceps as if larger weights were actually being used, which is an improvement over Broussard's device. However, Rae's device has the same fundamental disadvantages as Brousard's in that the second bar is placed in a fixed position relative to the position to which the weights are attached, which prevents the range of movements of the weights from being varied to change the amount of force that must be expended by the bodybuilder in performing curls and which allows the second bar to strike his forearms sharply at an intermediate point in the exercise.